met repeat aug 2013.doc

7/30/2019 met repeat aug 2013.doc

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1 Write short notes on following:a) Ice found near New Foundland

b) International Ice Patrol

c) Multiyear Pack Iced) Ice Limits in North Pacifice) Tabular type Ice bergs

(5 Marks each)

2 a) Describe Buyss Ballot law(5 marks)

b) Explain why it should not be used in certain places(5 marks)

c) Explain with reasons how you use Buys Ballots Law tofind the direction of the centre of a TRS.(15marks)

3 a) Describe the formation of radiation fog (09marks)

b) Describe the favorable conditions for Arctic Sea Smoke.(08 marks)

c) Explain the reason for frequent fog that you encounternear New Foundland (08 marks)

4. Describe the following clouds (5 markseach )

a) Stratusb) Cumulonimbus

c i) On a mountain range the windward side found to becool and wet while leeward side is warm and dry. With asuitable diagram explain the phenomena. (8marks)

ii) What type of clouds would you expect to form nearthe top of the mountain and the conditions required for it.(7 marks)


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5 a) What are the optimum conditions for a TropicalRevolving Storm to form. (10marks)

b) Describe the actions you would take once a TRS isconfirmed in the vicinity. (15 marks)

6. a) Describe Wind drift , Gradient and upwelling currents.(12 marks)b) Mark in the provided map the prominent currents in theAtlantic. (13 marks)


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Answers

1 Write short notes on following:A)Ice found near Newfoundland

Mainly the ice found near Newfoundland are Glacier type icebergs from the East Greenland west Greenland area. Theydrift down with the labror current to Newfoundland andmelts away once they are in the Gulfstream . Pack iceformed in arctic and the Canadian coast also could be foundin the area but the threat to ships from this is low as theyare not consolidated.

B)International Ice Patrol

The International Ice Patrol is an organization with thepurpose of monitoring the presence oficebergs in theAtlantic and Arctic Oceans and reporting their movementsfor safety purposes. It is operated by United States CoastGuard but is funded by the 13 nations interested in trans-Atlantic navigation. he organization was established in 1914

in response to the sinking of the RMSTitanic

. The primarymission of the Ice Patrol is to alert any seacraft traveling thegreat circle shipping lanes between Europe and the majorports of the United States and Canada of the presence of anyicebergs there.

C) Multiyear Pack Ice

The sea ice which has survived more than one summer arecalled multiyear ice. Their thickness is more than 2.0m.They

are danger to navigation. When the the multiyear ice notfast to ground that means when drifting it is called multiyearpack ice.

D) Ice Limits in North Pacific
http://en.wikipedia.org/wiki/Iceberghttp://en.wikipedia.org/wiki/Atlantic_Oceanhttp://en.wikipedia.org/wiki/Arctic_Oceanhttp://en.wikipedia.org/wiki/United_States_Coast_Guardhttp://en.wikipedia.org/wiki/United_States_Coast_Guardhttp://en.wikipedia.org/wiki/Sinking_of_the_RMS_Titanichttp://en.wikipedia.org/wiki/Sinking_of_the_RMS_Titanichttp://en.wikipedia.org/wiki/Great_circlehttp://en.wikipedia.org/wiki/Iceberghttp://en.wikipedia.org/wiki/Atlantic_Oceanhttp://en.wikipedia.org/wiki/Arctic_Oceanhttp://en.wikipedia.org/wiki/United_States_Coast_Guardhttp://en.wikipedia.org/wiki/United_States_Coast_Guardhttp://en.wikipedia.org/wiki/Sinking_of_the_RMS_Titanichttp://en.wikipedia.org/wiki/Great_circle


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In the north pacific , a line drown from the NE tip of theJapan , passing just north of Aleutian island , toapproximately 60 N , 160 W.

E) Tabular type Ice bergs

This is the most common form and is the typical iceberg ofthe Antarctic. These icebergs are largely, but not all, derivedfrom ice shelves and show a characteristic horizontalbanding. They may be of great size, larger than any othertype of iceberg found in either of the Polar Regions.

(5 Marks each)

2 a) Describe Buyss Ballot law (5 marks)

Face the true wind low pressure centre, in NorthernHemisphere ,is in the right side and in the SouthernHemisphere it is the left side.

b Explain why it should not be used in certainplaces (5 marks)

It is not accurate near the equator due to lack of coriolisforce and close to land as wind can be deflected off landfeatures.

c Explain with reasons how you use Buys BallotsLaw to find the direction of the centre of a TRS.

(15marks)

The direction of the centre is depend on the angle of indraftof the wind. In a TRS the angle of indraft varies as we getcloser to the centre. This happens because the wind


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becomes cyclostrophic near the eyewall due to high pressuregradient and the centrifugal force. In this case the centre lies8 points (AOI is zero)from the true wind direction .(to right inthe Northern Hemisphere and to left in the Southern

Hemisphere.).When in the outer storm area where with a comparativelylower pressure gradient ,the friction and coriolis force gives aan AOI of approximately 20 to 45 degrees. This makes thecentre to lie 10 to 12 points from the true wind direction.

3 a) Describe the formation of radiation fog

(09 marks)

Radiation fog is also called Land Fog, because it forms only

over land, not over sea. During the night, land gives off its

heat very quickly. On clear nights, the radiation of heat from

the land surface into space is quicker as it is unobstructed by

clouds. The air in contact with the ground thus gets cooled

and if cooled below its dew point, a large quantity of dew is

deposited. If, however, a light breeze is blowing, turbulence

causes the cold from the land surface to be communicated

to the air a couple of metres above the ground and shallow

fog called Ground fog results. The visibility at eye level

above this ground fog may be good but, in the fog, it may be

only a couple of hundred metres or less. If the wind is a bit

stronger, radiation fog may extend upto a height of about

150 metres or so above the ground. Strong winds cause too


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much turbulence resulting in low clouds (stratus type) and

no fog.

b Describe the favorable conditions for Arctic SeaSmoke. (08 marks)

When very cold, dry air passes over a relatively warm sea

surface, the water vapour, evaporating from the sea surface,

is quickly condensed into water-droplets and it appears as if

vertical streaks of smoke are rising from the sea surface.

This is called steam fog or arctic sea smoke as it is

commonly seen in the Arctic Ocean.

c Explain the reason for frequent fog that youencounter near New Foundland (08 marks)

This type fog is called the Advection Fog .It is formed

when a moist wind blows over a relatively cold surface of

sea or land. When the moist air is cooled below its dew

point, the excess water vapour condenses into small


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droplets of water on dust or minute particles of salt,

resulting in advection fog. Wind causes advection fog to

form and also to spread. If the wind is quite strong,

turbulence causes advection fog to form to considerable

depth. However, very strong winds carry the moisture too

high, resulting in low clouds (Stratus type) and no fog. On

the Grand Banks of New Foundland where the warm,

moist Westerlies, blowing over the warm Gulf Stream,

cross over the cold Labrador Current.

4. Describe the following clouds (2marks )

a) Stratus

This a low level layered cloud formed mainly when the

atmosphere is stable .b) Cumulonimbus (3

marks)

This is a cloud with great vertical extent.Forms when the the atmosphere is highlyunstable or in cold fronts. This extends fromsthe lower atmosphere to tropopause andsome time in horizontal direction to make

anvil shape. This brings heavy rains, thunderand lightning. Inside the cloud high turbulentwind is present.

c i) On a mountain range the windward side foundto be cool and wet while leeward side is warm anddry. explain this phenomena. (10 marks)


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Foehn winds are caused by the subsidence of moist air afterpassing a high mountain. The air is forced to move upslopewhen encounters a mountain barrier. As the temperature

decreases with height, the moist air will become saturatedand condense to form clouds and rain when it rises to acertain height. The amount of water vapour that remains inthe air therefore decreases. After passing the ridge anddescending along the leeside of the mountain, the airbecomes warmer. Temperature of drier air will rise evenfaster. This results in dry and hot winds.

ii) What type of clouds would you expect toform near the top of the mountain and the reasons for

that?(10marks)

If the atmosphere is stable and depending on weather thewind has reached its saturation then either stratus or altostratus would form near the top of the mountain. It is calleda table top cloud , if the atmosphere is unstable thencumulus type lumpy cloud would form.

5 a What are the optimum conditions for a TropicalRevolving Storm to form.(10 marks)

Sea temperature greater than 26C over a large area

raising air temperature and humidity.

Atmospheric instability due to high Environment Lapse

Rate.

Instability accentuated by high humidity increasingSaturated Adiabatic Lapse Rate.

Latitude greater than 5 where the Coriolis Force is

sufficient to provide vorticity, cyclonic circulation.

Low wind shear (change of wind speed with altitude) in

the troposhere permitting vertical development.


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Conditions permitting divergence of airflow at altitude,

removing air from the area and reducing atmosphericpressure.

A tropical disturbance to initiate the process. This is

likely to be convection associated with an easterlywave, the InterTropical Convergence Zone.

b Describe the actions you would take once a TRSis confirmed in the vicinity.(15 marks)

Action when approach of a TRS is confirmed

a) Obtain the bearing of the storm centre.b) Ascertain in which semi-circle the vessel lies.c) Take avoiding action.

a) Obtain the bearing of the storm centre:Face the wind, and according to Buys Ballots law,

the storm centre will lie 8 to 12 pints on your right inthe NH, left in the SH.

If the pressure has fallen 5 mb below normal, allow12 points as it means that either the vessel is in theouter fringes of a well developed TRS, or that a new

TRS is forming in the vicinity.

If the pressure has fallen 20 mb or more below

normal, allow 8 points as it means that vessel is nearthe eye of a well developed TRS.

WIND N. HEMISPHERE S. HEMISPHERE

VEERING Vessel located in Vessel located in

DANGEROUS SEMICIRCLE NAVIGABLE SEMICIRCLE

If pressure falling vessel in advance quadrant.

BACKING Vessel located in Vessel located inNAVIGABLE SEMICIRCLE DANGEROUS SEMICIRCLE

If pressure falling, vessel in advance quadrant.

STEADY If the pressure falling vessel in PATH


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Once the location of the vessel has been determined withinthe storm field, relative to its direction of movement, the

following action is recommended: -

6. a) Describe Wind drift , Gradient and upwellingcurrents. (12 marks)

WIND DRIFT

LOCATION N. HEMISPHERE S. HEMISPHERE

DANGEROUS Put wind on STB bow and a/c Put wind on portbow and

SEMICIRCLE to STB as wind VEERS a/c to PORT as windBACKS

(A)

NAVIGABLE Put wind on STB and a/c to Put wind on PORT anda/c

SEMICIRCLE PORT as wind BACKS to STB as windVEERS

(B) & PATH(C)


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Drift is the direct effect of wind blowing over long stretches

of ocean for long periods. The frictional effect of the wind, on

the sea surface, causes the sea surface to move. However,

Coriolis force deflects the drift current to the right in the

Northern Hemisphere (left in the Southern Hemisphere) by

about 300 to 450.

The maximum strength of a drift current is only up to about

2 knots. If, however, there are other strengthening factors

such as gradient, shape of the coast etc. The drift currentcan increase two or three fold and is then called a stream.

UP-WELLING

Whenever a wind blows away from a long coastline for a

considerable length of time, the outflow of water from the

coast is replaced by an upward movement (up-welling) of

sea-water, from a depth up to about 150 metres or so. Since

this up-welling takes place from below, the water that comes

to the surface is colder than the surrounding sea-surface.

Up-welling currents are experienced along the eastern

shores of oceans, in low latitudes. Here the trade winds blow

off shore, resulting in up-welling.

GRADIENT


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A gradient current is caused by differences in level (resulting

from natural slopes or build-up by winds) or by differences in

density (resulting from differences of temperature or

salinity). The greater the salinity, the greater the density and

vice versa. The lower the temperature, the greater the

density and vice versa.

When different water-masses lie adjacent to each other,

gradient currents are set up between them because ofdifferences in temperature and salinity.

b) Mark in the provided map the prominent currentsin the Atlantic. (13 marks)


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met repeat aug 2013.doc

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